1. Field of the Invention
The present invention generally relates to a contactor, in particular to a contactor contacting a terminal of a subject to be tested such as a semiconductor substrate (wafer), a wiring substrate, and an electrical component for performing electrical testing, a method for manufacturing such contactor, a method for contacting the wiring substrate using such contactor, and a testing method.
2. Description of the Related Art
Recently, with respect to semiconductor devices represented by an LSI (the semiconductor device is referred to as an LSI hereinafter), in order to accommodate the demands for down-sizing of a product to which the LSI is applied or for multi-functionalization of the product in case the size is the same as a conventional product, the wiring is increasingly arranged in more detail and also the circuit density is increasing. The finer arrangement of the wiring and the increase in the circuit density are accompanied by the increase in the number of terminals and the miniaturization of the terminals. Accordingly, the miniaturization of the contact electrode and the increase in the number of contact electrodes provided on the contactor (probe card) for testing the LSI in a wafer form are also demanded.
Previously, the LSI was usually tested and shipped in a packaged state but in recent years, more LSIs are tested and shipped in so called Known-Good-Die (KGD) state in which the LSI is tested in chip or wafer state without being packaged. The main reason for the sudden increase in the KGD is the increase 1) in the type of usage of so-called xe2x80x9cbear chip packagingxe2x80x9d in which the semiconductor chip is directly mounted to the substrate of the apparatus without being packaged (for downsizing) and 2) in the type of usage of so-called Multi Chip Module (MCM), or Multi Chip Package (MCP) or System In Package (SIP) in which a plurality of semiconductor chips is incorporated in a single package (for even more downsizing and multi-functionalizing).
In the manufacturing process of a semiconductor device for the type of usage as mentioned above, the testing items implemented in the conventional packaged state need to be implemented in the wafer or chip state. The terminal pitch of the wafer (chip) (mainly under 100 micrometers) with respect to the terminal pitch of the package (mainly 0.5 to 1.27 millimeters) is minute and the terminal size is also accordingly minute. Obviously, the performance of the testing contactor for the wafer is more demanding than that for the packaging.
Further, not only a peripheral terminal, which is predominantly manufactured conventionally, but also the number of manufactured area array terminals is increasing. The peripheral terminal is a pad terminal with an aluminum surface provided about the periphery of the chip for wiring the chip with a wire bond. The area array terminal is a terminal arranged in a grid shape on the chip area and a solder bump is mainly used as terminal material.
For a conventional peripheral terminal, a contact probe with an electrode contacting only the pad terminal arranged on the periphery of the semiconductor device is used. However, for the area array terminal, a contact probe having the ability to contact any position in the chip dimension is necessary.
Testing the LST in a discrete chip or in a packaged state is referred to as xe2x80x9ca discrete testingxe2x80x9d, whereas testing the LSI in the wafer state before cutting out into small pieces of LSI is referred to as xe2x80x9cwafer level testing.xe2x80x9d The wafer level testing tests the LSI after the wafer process and before the packaging, however, it includes the LSI applied with an additional process after the wafer process, such as the wafer level CSP packaged in the wafer state.
Also, the wafer which has been diced (cut) but still maintains the arrangement prior-to-cutting, due to being loaded on the dicing tape on which each chip is fixed and supported, may be considered to be included in the wafer level testing.
Since the wafer level testing allows the performance of testing without cutting the semiconductor wafer into the chips, the handling efficiency can be improved. Also, even when the size of the chip varies, since the wafer profile is fixed and standardized, testing equipment implementing the wafer level testing has a higher versatility than those implementing the discrete testing.
For the contactor (probe) for the wafer level testing, the following characteristics are required:
A) miniaturization of the terminal: A plurality of contact electrodes enabled to contact minute terminals arranged in narrow intervals is needed.
B) arrangement freedom: The plurality of contact electrodes can be arranged freely. In other words, the contact electrodes may be arranged not only around the periphery area but also as an array (grid). When all contact electrodes are arranged within the chip dimension, the chips adjacent to one another can be tested simultaneously.
C) widening of the contact area: Contact electrodes enabled to contact a plurality of LSIs at a time are required.
D) depressurization: Lessening the force applied to the thinner wafers, for example reducing the contact collective force, which is the summation of contact pressure of each contact electrode, with respect to the increase in the number of simultaneous testing or to increasing the number of pins of the LSI. For example, when the contact pressure of one pin is 10 g, the collective force for 50,000 terminals would add up to 5,000 kg.
E) cost reduction: The life cycle of the LSI wafer itself is becoming shorter. For example, in the case of general-purpose memory, the miniaturization of chips is performed approximately every 6 months and the terminal arrangement on the wafer is also changed. Also, more so-called ASICs specialized for particular customers and products are manufactured among the LOGIC products, and in particular, those for portable device applications have shorter life cycles. In view of the above, for the contactor (probe card) provided for each LSI wafer, the durability is important but also the contactor needs to be provided at a cost that pays off during a limited period of service.
With respect to the above-mentioned requirements, the prior art and the problems related thereto are listed below.
(I) Needle Method
1) Cantilever Method:
In this method, the needle point of a needle is registered with a terminal on the wafer and the other end of the needle is connected to the substrate. The interval of the terminals on the substrate side is larger than that of the terminals on the wafer side. Thus, the cantilever method has a constraint in terms of the terminal arrangement due to the configuration and therefore cannot address the requirement B) mentioned above. Also, this method has a constraint with respect to the requirement C). Therefore, since the terminals cannot be arranged as an area array or the dimension of the probe is larger than that of the chip, there exists a problem that the neighboring chips cannot be contacted simultaneously.
2) Vertical Probe Method:
2-1) Spring Probe (POGO-PIN) Method
With respect to the requirement A), the narrow pitch is structurally limited. In other words, the reduction of winding diameter of the coil spring has a limit. Also, with respect to the requirement D), in the depressurized state, stable contact cannot be obtained since there is no wiping motion so as to break the oxide film of the LSI terminals. Further, with respect to the requirement E), there exists a problem in that the spring probe is expensive due to the structural factors. In other words, it is necessary to wind the coil having a minute diameter separately. Also, a separate high precision boring component is necessary so as to maintain the position precision of the needle point.
2-2) Vertical Needle:
A conductive needle (rod-like member) rising in the vertical direction is set as a contact electrode. With respect to the requirement A), the displacement is caused by buckling and the direction in which the needle will bend cannot be determined in advance. Therefore, neighboring pins may contact and interconnect with each other. With respect to the requirement D), in the depressurized state, stable contact is unlikely to be obtained since there is no wiping motion.
3) Bending Needle Method:
With respect to the requirement A), depending on the degree of the bending, in order to arrange the bending needles at narrow pitches, the neighboring pins may obstruct each other. Also, with respect to the requirement E), the configuration in which each needle is bent individually is expensive.
(II) Membrane Method
With respect to the requirement A), since the contact electrodes are coupled together by an insulation substrate, when the pitch is narrow, the individual electrode cannot move freely. With respect to the requirement C), since the wiring extends between the contact electrodes, the amount of wiring is limited. Multi-layering of the wiring in the membrane method is advanced only to the degree of providing the wiring on both sides of the insulation substrate. With respect to the requirement D), in the depressurized state, stable contact is unlikely to be obtained since there is no wiping motion.
(III) Anisotropic Conductive Sheet (Rubber)
With respect to the requirement A), this sheet cannot accommodate narrow pitches. Also, there exist problems such as lack of heat resistance and durability.
As mentioned above, with the prior art, it is not possible to provide a contactor that meets all the requirements, i.e. A) miniaturization of terminals, B) arrangement freedom, C) widening of the contact area, D) depressurization, and E) low manufacturing cost.
In view of the problems mentioned above, an object of the present invention is to provide a contactor wherein the contact electrodes incorporating the bending needle method can be arranged at minute pitches and can be manufactured with low cost, and a method of manufacturing such contactor.
The contactor according to the present invention includes a wiring substrate and a plurality of contact electrodes formed on the wiring substrate. Each of the plurality of contact electrodes is a rod-like member with one end joined to the wiring substrate and the other end having at least two inclined planes, and an apex formed by the inclined planes deviating from the center of the cross-section of the rod-like member.
According to the present invention, when the plurality of the contact electrodes is brought into contact with a subject to be tested (for example, a semiconductor device), the contact electrode having two inclined planes buckles and deforms following the incline of the larger inclined plane among the two inclined planes. Therefore, it is possible to bend a plurality of contact electrodes in the same direction at the same time and thus even when the plurality of contact electrodes is arranged at narrow pitches, the contact electrodes do not contact one another.
To form two inclined planes having different dimensions is easy. For example, it can be achieved by making cuts to the rod-like member with two cutting tools. At this time, the displacement of the cutting tools is controlled so that one of the cuts is deep and the other one of the cuts is shallow thereby forming the two inclined planes with different dimensions. The two inclined planes having different dimensions may be achieved using two cutting tools having different cutting edge angles or having different thicknesses.
According to the present invention, the apex formed by the at least two inclined planes at the other end of each of the plurality of contact electrodes may comprise a cutting surface formed by the cuts and a fracture surface formed by tension fracture.
According to the present invention, since each of the plurality of contact electrodes has the one end joined to the wiring substrate and the other end comprising the inclined planes formed by the cutting surface and the fracture surface, each of the plurality of the contact electrodes may buckle and bend following the inclined plane formed by the cutting surface. Therefore, it may be possible to prevent the neighboring contact electrodes from contacting one another.
According to the present invention, each of the plurality of contact electrodes may be a bent rod-like member.
According to the present invention, the contact electrode may be obtained by depressing a depressing jig with a flat surface from above before placing the contact electrode in contact with the subject to be contacted and buckling the rod-like member to a certain direction with respect to the inclined plane. Thus, when the contact electrode contacts the subject to be contacted, even with small pressure, the contact electrode may deform in the direction to which the contact electrode is already buckled and deformed.
According to the present invention, the fracture surface of each of the plurality of contact electrodes may be a portion located farthest from the one end joined to the wiring substrate.
According to the present invention, the fracture surface may be located at the apex portion of the rod-like member and the inclined plane may extend downward from the fracture surface. In other words, by forming the cut at the position corresponding to the inclined plane and cutting off (fracturing) the rod-like member by tension after joining the rod-like member to the wiring substrate, the plane made by the cut may become the inclined plane and the fracture surface may be formed at the apex portion of the inclined plane.
According to the present invention, the rod-like member may be a non-conductive member having a conductive coating formed at its surface.
According to the present invention, the non-conductive member may be used as the rod-like member and thus a contact electrode with various characteristics may be created.
According to the present invention, the rod-like member may be a metal wire and the metal wire may have a conductive coating formed at its surface.
According to the present invention, metal wire for wire bonding, for example, may be used as the rod-like member. In such a case, a wire-bonding device may be used to easily join the contact electrode to the wiring substrate. Also, by changing the type or the thickness of the conductive coating, a conductive electrode with various characteristics may be created.
According to the present invention, the position of the other end of each of the plurality of contact electrodes may be displaced by a predetermined distance in a direction parallel to the surface of the wiring substrate with respect to the position of the one end joined to the wiring substrate.
According to the present invention, when the apex portion of the contact electrode is depressed, the apex portion may move along an oscillating path. By doing so, a so-called wiping motion where the apex portion of the contact electrode moves over the contacting portion of the subject to be tested may be achieved and thus a good contact may be obtained.
The method of manufacturing a contactor according to the present invention comprises the steps of: joining one end of each of a plurality of conductive rod-like members, having the other end formed with an inclined plane, to a wiring substrate; and depressing the apex portion of the inclined plane with a flat surface of a depressing member so as to bend the plurality of conductive rod-like members, thereby forming a plurality of contact electrodes.
According to the present invention, by depressing the apex portion of the inclined plane with the flat surface of the depressing member, the plurality of the rod-like members may be buckled to a determined direction with respect to the inclined plane. The plurality of contact electrodes formed in such method may be arranged at narrow pitches. Also, since the plurality of contact electrodes has a small spring constant, they are suitable for testing a semiconductor device having narrow-pitched electrodes or a semiconductor device of the wafer level.
According to the present invention, the method may further comprise a step of forming a cut on the conductive rod-like member. The step of forming the cut may be performed at a position different from the position where the step of joining the conductive rod-like member to the wiring substrate is performed.
According to the present invention, since the conductive rod-like member is joined to the wiring substrate after the cut is formed on the conductive rod-like member, the interference by the cutting tool to the conductive rod-like members already joined to the wiring substrate may be prevented.
According to the present invention, each apex portion of the plurality of conductive members may be depressed by the depressing member, each apex portion being inserted in a corresponding concave portion provided in the depressing member.
According to the present invention, since the plurality of the rod-like members is bent having the position of each apex portion of the plurality of rod-like members controlled by the position of the corresponding concave portions of the depressing member, the apex portion of the rod-like member may be arranged with high accuracy.